The invention relates to an electrical circuit having at least one electrical component, in particular a strain-sensitive resistor, and conductor tracks which are applied to a metallic carrier with the intermediate positioning of at least one insulating layer.
An electrical circuit which is used essentially as a strain gauge has been disclosed, for example, by DE 197 47 001 C2. Sensors with strain gauges are used, inter alia, in motor vehicles, for example for measuring the torque at the steering wheel. However, in such sensors stringent requirements are made in terms of the electromagnetic compatibility.
The object of the present invention is therefore to improve the known electrical circuit in terms of the electromagnetic compatibility.
This object is achieved according to the invention in that at least one further conductor track is applied to the surface of the metallic carrier and is connected to at least one conductor track of the circuit.
The circuit according to the invention has the advantage that the metallic carrier, in particular the steel carrier, is used as a grounding layer. In addition, the circuit according to the invention has the advantage that thermal stressing of the steel associated with the application of further layers is avoided because said steel is electrically conductive and thus serves itself as a grounding layer. As a result of the avoidance of the additional thermal loading, the steel maintains its mechanical strength values, in particular pulling strength, tensile strength and breaking strength.
In order to bring about a secure connection between the circuit and the steel substrate, one advantageous refinement of the invention provides for the at least one further conductor track to be arranged between the at least one insulating layer and the metallic carrier, and for at least one conductive feedthrough to be provided from the further conductor track to the at least one conductor track.
Another advantageous refinement advantageously safeguards this connection by virtue of the fact that the at least one further conductor track is applied to the metallic carrier next to the at least one insulating layer, and that the at least one further conductor track is connected to the at least one conductor track using a connecting conductor track which runs over the surface of the at least one insulating layer.
The invention can also be applied in metallic carriers composed of materials other than steel. The conductor tracks are preferably composed of silver. However, other conductive materials, in particular gold, silver platinum, silver palladium or copper are also suitable.
One advantageous method for manufacturing the first embodiment takes the form of the at least one further conductor track being applied on the metallic carrier as a low-impedance conductor track paste, the at least one insulating layer then being applied as a dielectric paste leaving vias exposed, and the at least one conductor track which is to be connected to the further conductor track being then applied with a conductor track paste which penetrates the vias.
The second embodiment can preferably be manufactured by applying the at least one insulating layer on the metallic carrier leaving exposed the surface which is provided for the further conductor track, and a low-impedance conductor track paste being then applied to the surfaces which are provided for the conductor tracks and for the at least one further conductor track, including the connecting conductor track.